The present invention, in some embodiments thereof, relates to detecting systems, and more particularly, but not exclusively, to a device and method useful for detecting certain concealed and non-visible substances, possibly at low amounts thereof.
In many public and commercial establishments there is a need to detect the presence of harmful or illegal substances in order to maintain public order, safety, and/or health. Some examples from the field of security include the detection of hidden explosives, hazardous materials, and/or illegal narcotics transported by criminals and terrorists, either on their body or in luggage or cargo. Some health and safety examples include the detection of unsafe levels of air pollution, toxic gases in an industrial environment, and pesticides at a food production/processing facility. Often more than one type of substance needs to be detected. For example, at airports and border crossings security personnel seek to intercept both explosives and illegal narcotics.
The development of an automated substance detector raises a number of technical issues. For example, the substances to be detected may have physical characteristics and chemical signatures that vary over a very wide range. In some cases the parameters to be detected may be extremely low. For example, some plastic explosives and narcotics, particularly when sealed in luggage, have vapor pressures measured in parts per billion or trillion, which is so low as to be virtually undetectable by conventional instrumentation. In order to check people in transit, the detection needs to be not only accurate but also continuous, quick, safe, and unobtrusive. It is also beneficial for such a system to be relatively low cost and compact, so that it may be cost-effectively deployed at sites that are usually unguarded or that have comparatively low traffic, such as schools and shopping centers.
Radiation technology such as x-rays or gamma rays is sometimes employed to detect concealed explosives and drugs. This technology however cannot be used to check people because of the harmful effects of radiation on health. It is also relatively inaccurate, because it can only identify the specific weight or outline of a shape of detected objects, or spectral behavior of some substances, under limited conditions. This result often at most informs the operator that objects have been detected that are potentially dangerous, and accordingly falls short of the more definitive assessment generally required to efficiently process the movement of multiple objects in real time.
Another approach, sometimes called “smeller” technology, takes an actual physical sample from the person or object being checked and/or from his immediate vicinity. The sample is analyzed to determine its chemical composition or the presence of ions of the prohibited items, such as explosives or drugs. Examples of this technology include ion mobility spectrometry and gas chromatography. Smeller systems however are generally costly and complicated to operate. Further, they can have trouble checking a continuous flow of people or objects due to the need to take samples and to be re-set between subjects.
Some attempts have been made in the art to provide automatic detectors of explosives and narcotics. Vandrish, U.S. Pat. App. 2006/0081073, shows an examination station equipped with several air jets and corresponding collection ports. Detection occurs by directing pressurized air at the subject, collecting and concentrating the air in a device such as a cyclone, and producing samples for chemical analysis. The main analysis method described is chemiluminescence, in which luminol reacts with NO2 to produce optically detectable light.
Kardish, U.S. Pat. No. 5,648,047, shows a handheld manual device suitable for use by non-skilled operators. The device has an enclosed housing, a roll of substrate, and one or more reagents that can be selectively dripped onto the substrate inside the housing. A sample is taken by wiping a surface of an object to be tested on a clean segment of the substrate. The segment is then rolled to a position where the reagents can be dispensed. If explosive or narcotic chemicals are present, a reaction will occur which produces a color change (colorimetric detection) in the substrate that can be viewed by the operator.
Baumann, U.S. Pat. No. 6,978,657, shows a portable device having a metal fiber or sheet substrate. A sample is deposited on the substrate by shooting a jet of gas on the object being tested or by directly wiping a surface of the object with the substrate. The substrate is heated, and a reaction takes place if the tested chemicals are present. A gas is then passed over the substrate to carry the heated sample to a detector.